This invention relates generally to a new and improved Stirling cycle machine, and more particularly relates to a new and improved Stirling cycle machine providing increased accessibility to the coldest internal portion of the machine and decreased wear of the bellows providing the variable volume compression and expansion chambers of the machine.
As known to those skilled in the art, Stirling cycle machines employ the well known Stirling cycle to provide very low temperatures for cooling objects such as, for example, electronics. As is further known, Stirling cycle machines include variable-volume compression and expansion chambers interconnected by a regenerator for conducting gas between the chambers. Some prior art Stirling cycle machines use pistons and cylinders to provide the variable-volume compression and expansion chambers while other prior art Stirling cycle machines use bellows to provide the variable-volume compression and expansion chambers. The Stirling cycle machines using the bellows also use driving means for imparting upward movement to the bellows to compress the chambers which chambers are compressed and expanded out of phase with each other, for example 90.degree. out of phase.
As is still further known to those skilled in the art, in the typical prior art Stirling cycle machine utilizing such bellows, the bellows are driven by eccentric drive means which impart upward movement to the bellows to compress them, but it has been found that such prior art eccentric drive means typically also unwantedly impart at least some rocking motion, side thrust, or lateral movement to the bellows along with the upward movement which undesirably increases the wear of the bellows and unwantedly shortens the life of the bellows and thereby the life of the Stirling cycle machine. It has been found that even when the bellows are contained within a tube or cylinder for restricting the bellows movement generally to upward movement, there is still at least a tendency with the prior art eccentric bellows drive to also impart at least some rocking motion, lateral side thrust or lateral movement to the bellows which causes undesired increased wear of the bellows and unwanted shortened machine life. Shortened bellows life and therefore shortened machine life is a problem attendant to the typical prior art Stirling cycle machine employing eccentric bellows drive means.
As is further known to those skilled in the art, the regenerator of a Stirling cycle machine is said to have a hot end and a cold end and the coldest internal portion of the Stirling cycle machine is the cold end of the regenerator which is connected to the expansion bellows providing the variable-volume expansion chamber. Further, typically, the connection of the cold end of the regenerator to the bellows providing the variable-volume expansion chamber is buried deep within the interior of the Stirling cycle machine making the cold end of the regenerator extremely inaccessible for the mounting thereto of an object to be cooled such as the above-noted electronics. This inaccessibility is also a problem attendant to the prior art Stirling cycle machines.
An example of a prior art Stirling cycle machine using bellows to provide the compression and expansion chambers is disclosed in U.S. Pat. No. 4,619,112, patented Oct. 28, 1986, Stirling A. Colgate inventor. The Stirling cycle machine disclosed in this patent includes compression and expansion chambers which may each comprise an isothermal bellows disclosed in U.S. Pat. No. 4,490,974, patented Jan. 1, 1985, Stirling A. Colgate inventor. The above-noted prior art problems attendant to the typical prior art Stirling cycle machine may be better understood by reference to FIG. 8 of the U.S. Pat. No. 4,490,974; in FIG. 8 of this patent, it will be noted that the bellows defining the compression chamber 1 is driven by a single eccentric including a crank 6 mounted on the rotatable shaft 8 and that the bellows defining the expansion chamber 2 is driven by a pair of eccentrics including crank arms 7 also mounted on the rotatable shaft 8. Thus, it will be understood that in this prior art Stirling cycle machine bellows eccentric driving mechanism, even though the eccentric driving apparatus are confined within structure to cause them to impart upward movement to the bellows, since the drives are eccentric drives, there is at least a tendency to impart at least some side thrust, rocking motion, or lateral movement to the bellows along with the upward movement.
Further, as is illustrated in FIG. 8 of the U.S. Pat. No. 4,490,974, the coldest internal portion of the machine, that is the cold or upper end of the regenerator 3, is buried deep within the interior of the machine with the cold or upper end of the regenerator 3 being connected to the bottom portion of the expansion chamber 1 also buried deep within the interior of the Stirling cycle machine. This deep burying makes it extremely difficult to mount and remove objects to be cooled. Accordingly, there exists a need in the Stirling cycle machine art for increased accessibility to the internal portion of the machine where the cold end of the regenerator connects to the bellows providing the variable-expansion chamber, and for improved eccentric drive means reducing bellows wear wherein the upward movement imparted to the bellows is imparted with at least a reduced tendency of also imparting side thrust, rocking motion, or lateral movement to the bellows.